Nowadays, smart phones, tablet computers or other portable electronic devices are mostly equipped with miniature camera modules for a user to take pictures or photographs. The main components of the camera module employed in the portable electronic device includes a lens for focusing light, and an image sensor. When taking a picture, light reflected by an object will pass through the lens and is focused on the image sensor. The image sensor, in turn, will convert an optical signal into an electrical signal that is operable to become a digital image.
To prevent the image sensor from being affected by infrared rays or the like which will lower the quality of the digital image, a filter mounted on a frame is usually disposed between the lens and the image sensor to block passage of, for example, the infrared rays. To avoid the frame from blocking the focused light, and in consideration of the component tolerances and assembly errors, the area of the filter must be greater than an effective light sensing area (light imaging area) of the image sensor.
Under some circumstances, peripheral components of the image sensor, such as gold wire for chip mounting and wire bonding, etc., will reflect the light entering an interior of the camera module to a surface of the lens which is proximate to the image sensor, and then the light is focused on the image sensor, thereby causing the quality of the digital image to lower. The light reflected in the interior of the camera module is called flare. To resolve the problem of lowering the image quality caused by the flare, an anti-reflection film layer is usually coated on a surface of the lens to reduce formation of the flare, or a black ink layer is printed on a region of the filter by an oil printing method to shield the flare.
However, the technical barrier and the cost of providing blank ink layer on the filter are high and are not easy for later adjustment and correction. Hence, there is still room for improving the conventional filter.